Nails used in power operated nailing applicators are preferably formed into strips, being joined together by for example glue, adhesive stripping, or in some cases wires have been welded to the shanks. It is desirable that the strips shall have a predetermined length suitable for the nailing applicator. At the same time, it is desirable that the strip shall contain as many nails as possible within that given length. This will reduce the down-time involved when reloading the nailing applicator magazine with a new strip of nails.
For this purpose, the nails in the strip are arranged with the nail heads overlapping one another. The nails are offset with their heads one above the other, so that the axis of the strip is more or less diagonal to the axis of the nail shanks. With a strip formed of conventional round headed nails having circular heads with the head centre coaxial with the nail shank, the edge of the head of one nail will interfere with the shank of the next adjacent nail, causing the nails in the strip to be spaced apart. This spacing increases the difficulty of joining the nails together into the strip. In addition however it reduces the number of nails which can be accommodated in a strip of a predetermined length.
It is, however, desirable to maximize the number of nails which can be accommodated in a strip of a given length. This will mean that the magazine of the nailing applicator, which usually will accept a strip only of a certain predetermined length, will carry a greater number of nails. This in turn will reduce the down time of the nailing applicator, since it can be operated for a longer period of time, without the magazine requiring a refill.
For this reason, in the past nails have been made with "heads" which are shaped in plan more or less in the shape of the letter D. In this way, the nail shanks could lie against one another, with the heads overlapping one another, but without interfering with the shanks. This solution appears to satisfy the objective of maximizing the number of nails in a given length of strip. The total area of the nail head is somewhat reduced, as compared with a circular headed nail. This is sometimes perceived to reduce the ability of the nail head to resist penetration into a workpiece, such as a piece of wood. This problem is reduced if care is taken to ovient the nail head across the grain of the wood. If the nails are incorrectly positioned there may be a tendency for the applicator to drive the nail too far into the work piece. In addition, there may be a tendency for the nail head to pull through one of the wooden work pieces.
To alleviate this problem, it is proposed, in U.S. Pat. No. 5,056,976 H. Sygnator et. al., dated Oct. 15, 1991, to provide a nail with a circular head, with the centre of the circular head offset relative to the axis of the nail shank, so that the periphery of the circle of the head, at one point, coincides with the periphery of the nail shank. In this way, it is proposed, that the nails can be closely collated into a nailing strip, with their shanks in virtually edge abutting relation and with their heads overlapping, and at the same time there is no loss in the holding power of the head itself. There are however various practical difficulties with this proposal. Since the centre of the circular nail head is substantially offset from the axis of the shank, there is a tendency for such nails to cause difficulties when used in a standard power operated nailing applicator. The problem lies in part in the design and manufacture of the standard nailing applicators. The nailing driver, reciprocates in a guide, and the nail is held in the guide until the driver hits the nail head. However, the holding of the nail in the guide is achieved by the junction means joining the nails and forming then into a strip. Since the nail head is circular, and is substantially offset from the nail shank, the nail head projects across the guide but with the shank offset to one side. As a result, the nail shank will lie close to side wall of the guide, and in fact the head, and shank may cause excessive wear to the guide, or may cause the nail to be damaged when it is driven in, since the shank is offset away from the axis the driver itself.
There are also practical problems in manufacturing circular nail heads which are so substantially offset from the axis of the shank from which the nail head is formed. In spite of the shortcomings of this proposal however, it is still clearly desirable to maximize the area of the nail head in this type of nail, provided that this can be done both without reducing the number of nails which can be formed into a strip of a given length, and also which can be done without interfering with the operation of the power operated nailing applicator.